Method of producing gaskets from polyurethane/urea compositions and

Abstract

The present invention is directed to a method of forming a gasket around a substrate from a novel polyurethane/urea composition via the RIM process. Window gaskets may be produced by this method. These novel polyurethane/urea compositions comprise the reaction product of a (cyclo)aliphatic polyisocyanate having a viscosity of less than about 25,000 mPa.multidot.s at 25.degree. C. and a NCO functionality of 2.0 to 4.0 with an isocyanate-reactive component comprising b1) a relatively high molecular weight organic compound containing hydroxyl groups, amine groups, or mixtures thereof; and b2) a low molecular weight chain extender selected from the group consisting of diols, primary amines, secondary amines, aminoalcohols, and mixtures thereof; in the presence of a catalyst. The isocyanate and isocyanate-reactive components are selected such that the crosslinking density of the resultant polyurethane/urea composition is at least 0.3 moles/kg. It is also possible that the isocyanate-reactive component comprises b3) a low molecular weight chain terminator, and/or b4) a low molecular weight crosslinking agent. When either or both of these components are included in the isocyanate-reactive component, A, b1), b2), and/or b3) and/or b4) must be selected such that the crosslinking density of the resultant polyurethane/urea composition is at least 0.3 moles/kg.